1. Field of the Invention
The present invention relates to the field of synchronizing asynchronous signals and finds particular use in synchronizing video type signals in television systems.
2. Description of the Prior Art
The prior art contains many circuits for video synchronizers, beginning with U.S. Pat. No. 4,018,990. These synchronizers generally provide video synchronization by sampling and digitizing the active video portion of a video signal in response to the timing thereof, storing the digitized video in a memory, reading the digitized video from the memory at a proper time in response to a reference signal to achieve synchronization thereof, converting the read digitized video back to analog, and reconstructing and combining sync, burst and blanking with the read analog video.
Various techniques and circuits to perform these functions are well known in the art, and emphasis has been placed on improving performance in terms of minimizing noise and distortion from the digitizing process, and improving the immunity of the devices to noise which may be carried with or interfere with the signal which is being synchronized.
The inventive video synchronizer and improvements described herein are designed to allow synchronization of high quality video like signals in analog or digital form (which may include compressed digital form such as MPEG, etc.), while providing minimum distortion and maximum transparency. The invention is particularly well suited for efficiently synchronizing multiple video type signal of mixed or matched form to a desired reference signal. It will be recognized that the inventive teachings herein may be applied equally to analog signals in analog component, composite, serial and parallel and digital data streams in digital serial, parallel, component, composite and compressed forms, as well as other forms and standards of electronic signal conveyance.
Because full sync tip to peak white video is digitized in the analog preferred embodiment shown herein, one would normally expect quantizing errors to be significant. The inventive features of the preferred analog embodiment however show the use of sophisticated digital signal processing techniques such as over-sampling and interpolation, such that these errors are kept to unexpected low levels.
The inventive concepts described herein are applicable for many analog and digital video signal standards, including but not limited to MONOCHROME, SECAM, PAL, NTSC and HDTV versions in analog form, for example the well known RS-330 and RS-170 standards, as well as digital forms, for example the well known SMPTE 259 and 260 standards, or compressed digital form, for example JPEG, MPEG 1 and MPEG 2.
Other functions may be combined with the synchronizing function, for example standards conversion, compression and decompression, noise reduction, oversampling and filtering. Such additional functions will be referred to herein and in the claims as filtering, and will be understood to include such additional functions.
In the preferred embodiment of the invention it is taught to store and pass one or more secondary signal with the video signal in a fashion which maintains proper time relationship between the video signal and the secondary signal.
The preferred embodiment is suitable to be constructed on a single small, low power PC board which because of small size and low power may be installed in various case configurations. It is also shown to pass one or more secondary signals with the video signal in a separate parallel but time related path.
The inventive concepts described herein are well suited for use in synchronizing satellite feeds, inter-suite connections and in house signals, thus eliminating the use of expensive and cumbersome multiple genlocking and timing schemes.
Objects of the invention include:
An improved video synchronizer designed to allow synchronization of high quality video like signals while providing minimum distortion and maximum transparency.
A synchronizer which maintaining high signal quality at a reasonable price.
A synchronizer which digitizes full sync tip to peak white video with low quantizing error and distortion.
A digital signal device which makes use of oversampling and interpolation, such that sampling and quantizing errors are kept to unexpected low levels.
A video synchronizer which may be constructed on a single PC board and which may be installed in various case configurations.
A multiple signal synchronizer configuration in which a single genlock circuit may be utilized to provide reference signals for multiple synchronizers, but still retain individual genlock phase controls for each.
A signal synchronizer to use the input signal as the reference to allow the synchronizer to be used as an adjustable, fixed length delay, which use may be automatically switched.
A signal synchronizer capable of using recursive and nonrecursive adaptive filtering for noise reduction, image enhancement or other features.
A signal synchronizer capable of storing a full repetition period of the signal in memory.
A video signal synchronizer capable of digitizing and storing the entire video signal, including all sync, burst, horizontal blanking and vertical blanking so as to pass all signals encoded outside the active video area.
A video synchronizer capable of selecting ones of the signals contained within the blanking areas, so that those signals may be preserved and passed with only the repetitive sync burst and blanking reconstructed and reinserted in the stored signals from the memory.
Video signal processing having a memory for storing the video signal and having a parallel storage path for use in video or television systems for the passing of one or more related or unrelated secondary signals with the video signal in order to maintain separate parallel but time related transmission paths for the secondary signals.
A synchronizer for video type signals in which reduction in size and power consumption is brought about by minimizing the electronic circuitry.
A video synchronizer for multiple video signals of the same or different form for which the circuitry for each video signal may be separately constructed and which may be installed in various case configurations, with the common circuitry being shared by the multiple circuits.
A signal synchronizer in which one of the input signals is used as the reference.
A multiple electronic signal synchronizer which is configured to be used as an adjustable, fixed length delay, which use may be automatically switched.
A multiple signal synchronizer configured to use a selected one of the input signals as the reference to synchronize a plurality of input signals to one of the plurality, with the selection of the reference being automatically switched under known conditions.
A signal synchronizer capable of storing a full repetition period of the signal in memory.
A video signal synchronizer capable of storing the entire video signal, including associated sync, timing, error checking and ancillary signals or portions so as to pass those signals or portions in addition to the active video portions.
A video synchronizer capable of selecting ones of the portions outside of the active video so that those portions may be preserved and passed or reconstructed and reinserted in the stored signals from the memory.
A video signal processing device having a memory for the video signal and having an additional memory capability for one or more related or unrelated secondary signals in order to achieve proper time relationship of the secondary signals with respect to the associated video signal.